Spark-plug



C. C. SNODGRASS.

,SPARK PLUG.

APPLICATION FILED MAR. 5. 1919.

1,341,221 Patented May 25, 1920.

FIGC! FIG. 2

UNT STTES CHARLES C. SNDGRASS, 0F P'LTSBURGH, ?E\TNSYLVH.

Application filed March 5,

To all who/1t 'it may (fonce-2"" s lie it known that l, Crmnnss C. SNonunnss, a citizen ot' the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Spark- ?lugs; and l do hereby declare the following to be a full, clear, and exact description thereof.

My invention relates to spark-plugs for internal combustion engines.

The object of my invention is to provide a simple and durable form of spark-plug in which' provision is made for. taking care of expansion and contraction which takes place under the higher temperature caused by the continual explosions taking place in the cylinder lofthe engine, thereby-protecting the porcelaine from cracking and causing a short-circuit. My improved spark-plug is particularly adapted for use in aeroplane engines subject to the sudden changes in temperature in passing from a low to a high altitude.

ln the accompanying drawing, Figure 1 is an elevational view of my improved spark-plug; Fig. 2 is a longitudinal vertical sectional view, and Fig. 3 is an inverted plan view.

Referring to the drawing, the numeral 2 designates the outer shell or casing having the internal shoulder 3 which forms a support for the lower porcelain 4, a copper-gasket 5 being interposed between said shoulder and the shoulder 6 formed on said porcelain.

`Within the lower porcelain and cast inl tegral therewith is the electrode-rod 7, said electrode-rod having at the lower end thereof the diskS.

An aluminum gasket 9 surrounds the lower porcelain 4, and a castellated jam-nut 10 is screwed into the upper end of the casing 2 and locks said lower porcelain 4f securely within said casing 2. l prefer to use a castellated jam-nut 10 as it may be screwed. into place by an ordinary Spanner which can be operated more conveniently and with less danger of breaking the porcelain than an ordinary Wrench.

The upper porcelain 11 has the stud or projection 12, which enters the seat in the upper end of the lower porcelain 4l, oetween'the shoulder 14# the upper porcelain 11 and the upper end ci? the lower porcelain an insulating'washer 15 is interposed, said washer lacing formed et? mica or other Specification of Letters Patent.

Patented May 25., '1924).

1.919. Serial No. 30,'06.

suitable material. A space 16 is left between the lower' end of the stud 12 and the bottom of the seat 13 to allow for expansion and contraction of the porcelaine independently of each other.

The electrode-rod 7 passes up through the upper porcelain 11 and a knurled-nut 17 is screwed to the upper end of said electroderod.

A cap 18 tits over the top of the upper porcelain 11, and between said cap and knurlednut 17 is the lock-nut 19.

rlhe firing points 20 preferably made of tungsten steel are inserted through the walls of the shell or casing 2 at a proper angle, said ring points being preferably three in number and properly spaced with reference to the disk 8, likewise preferably formed of tungsten steel. Y

The washer 15, interposed between the upper and lower porcelains, acts as a cushion to take care of expansion and contraction which takes place under the high temperature caused by the continual explosions tak` ing place in the cylinders of the engine, thereby protecting the porcelains from cracking and causing short-circuit. As the expansion and contraction takes place rapidly above the shell 2, the upper porcelain is more liable to break, especially in the case of aeroplane engines, where if a plane is ,ying low on a warm day, the porcelain becomes very hot, and where a sudden Hight is made to a very high altitude, the temperaturasometimes changes from 60 to 7 OO l?. to zero or below in a few minutes, and as the upper porcelain is exposed to the air currents. l have made provision `for taking care of these sudden changes by forming the upper porcelain separate from the lower, so that it can expand and contract independently of the lower porcelain. The lower .porcelain inclosed as itis in the shell or casfrom the porcelain, and the cool air from the engine cooling ian carries oft" the heat from said disk, causing the temperature to remain low. The said disk 15 also may be termed a high tension insulator, as it is impossible the current to are from the top of the dry and giving the currentno path in which to travel to cause a sliort-circuitfand'resulting in the engine missing fire.

The disk l5 also affords the protection to the porcelain when putting the plugin or removing it from the `engine, for it the wrench should slip as it may often do, it will strike the disk first, thereby breaking the blow and saving the porcelain.

Another important feature of my invention is that both the uppei' and lower porcelains can be removed from the shell'with out unscrewing the shell .from the 'engine cylinder. the shell by the jam-nut l() which forces the porcelain down against the gasket 5 resting on the shoulder 3, pressure being applied to the conical shaped portion of the lower porcelain through the jam-nut l0 forcing the aluminum gasket 9 against said conical seat.

They are held firmly in place inA lVhat I claim is:

l. In a spark-plug, the combination of a suitable shell or casing, a lower porcelain supported therein, an upper and separate porcelain connected to said lower porcelain, saidupper porcelain being entirely above sa'id shell or casing, and a disk of insulating material interposed between said porcelains and extending beyond the greatest diameter of said lower porcelain.

2. In a spark-plug, the combination of a suitable shell or casing, a lower porcelain supported therein, said lower porcelain projecting above said shell or casing, and having a recess formed therein, an upper and separate porcelain having a projection entering said recess, and an insulating disk interposed between said poicelains.

In testimony whereof I, the said CHARLES C. SNonGRAss, have hereunto set my hand.

CHARLES C. SNODGRASS.

Witnesses Ron'r. D. ToTTEN, SARAH F. ARMSTRONG. 

